Abstract: SiC_w/Al_2O_3 ceramic composites were successfully prepared by in-situ carbothermal synthesis using gaolinite nano carbon black as raw material. Effects of synthesis temperature, holding time, material ratio and the flow rate of argon atmosphere on products were studied, and the reaction mechanism was also discussed. The synthesized products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that pure and uniformly distribute SiC whiskers and Al_2O_3 particles ceramic composite powder can be obtained at 1500 ℃ for holding 2 h when the molar ratio of kaolinite/carbon was 1/8 and the argon flow was 80 mL/min. The SiC whiskers displayed an ideal aspect ratio of more than 20 with a length over 6 μm and a diameter 300 nm. The carbothermal reaction of kaolinite was included two stages: the carbothermal of SiO_2 and the carbothermal of mullite, the growth mechanism of SiC whiskers is V-S mechanism.